biology part 2, biology harder Flashcards
Mitosis
Most body cells have two copies of each chromosome
We describe these cells as diploid
mitosis proceses
They have DNA
it gets replicated
They split
What is mitosis important for
replacing cells
Allowing growth
stem cells
Many tissues in the human body contain a small number of unspecialised cells called stem cells
importance of meiosis
Production of gametes e.g. sperm cells and egg cells, pollen grains and ovum
increases genetic variation of offspring
Mitosis in a nutsheel
two cells produced (daughter cells)
Daughter cells are diploid and identical to each other and the parent cell
One cell division occurs
meiosis in a nutshell
Four cells produced (daughter cells)
daughter cells are haploid, different from each other and the parent cell
Two cell divisions occur
Asexual reproduction
Mitosis Genetically identical single organism can reproduce No fusing gametes quicker
sexual reproduction
Meiosis Genetically diverse Mate Fusion of gametes diploid formed from 2 haploid Takes longer
What uses asexual reproducition
Spider plants
tubers
Bulbs
What does the fusion of gametes form
A zygote
what reproduction is more efficent
Asexual
define the term meiosis
cell division
chromosome number halved/diploid to haploid
State the name of the type of cell division that produces gametes
Meiosis
which cell is produced by meiosis
sperm
Define the term mitosis
cell division to give two identical cells
two examples of when mitosis occurs
Asexual reproduction
Growth of tissue`
What is produced when a cell undergoes mitosis once?
two new cells which are identical to each other and to their parent cell
Flowers
the reproductive organ of the plant. Contains female and male reproductive parts
Produce pollen which contains a nucleus inside the is the male gamete
how are plants pollenated
This process is known aspollinationand there are two main mechanisms by which it occurs: transferred byinsects(or other animals like birds) or transferred bywind
The structure of insect and wind-pollinated flowers are slightly different as each is adapted for their specific function
Parts of the flower
sepal Petals anther Stigma ovary Ovule
speal
Protects unopened flower
anther
Produces and releases the male sex cell
stigma
Top of the female part of the flower which collects pollen grains
ovary
Produces the female sex cell (OVUM)
Ovulee
Contains the female sex cells
insect pollinated flowers:
Insect pollinated flowers producesmaller amountsoflarger, heavierpollen grains that often containspikes or hookson the outside so they are better able to stick to insects
Wind pollinated flowers
producelarge amountsofsmall, lightweightpollen grains that are usuallysmooth
When does fertilisation occur
when apollen nucleus fuses with an ovum nucleusin the ovule
Pollination vs fertilisation
after sex, the male sex cells (sperm) have been deposited into the female. But, for fertilisation to occur, the nucleus from a male sperm cell has to fuse with the nucleus of a female sex cell (egg) and the sperm has to travel to find the egg before this happens. It’s exactly the same in plants!
Factors affecting germination
Water– allows the seed to swell up and the enzymes in the embryo to start working so that growth can occur
Oxygen– so that energy can be released for germination
Warmth– germination improves as temperature rises (up to a maximum) as the reactions which take place are controlled by enzymes
does carbon dioxide make a difference for germination
No, it makes no difference
Prostate gland
produces fluid called semen that provide sperm cells with nutrients
Sperm duct
sperm passes through sperm duct to be mixed with fluids produced bu the glands before being passed into the urethra for ejaculation
Urethra
tube running down the center of the penis that can carry out urine or semen.
Testes
produces sperm, stored in scrotum
penis
passes urine out of the body from the bladder
Oviduct
connects to ovary to the uterus
